It's recommended to keep decks with a Plot at 51 (unless you're checking in multiple decks) as decks not at least 50 cards are no longer tournament-legal.
You're correct, but I don't think he's talking about legality, but simply strategy.
Yes, if you have the funds making 3 identical decks will obviously give you the biggest edge, now you can use 3 plots, instead of 1, at a tournament. And to mess with people.
